Trapped ions masquerading as high-speed particles have been used to confirm a bizarre 80-year-old prediction of quantum mechanics.

Quantum particles racing at close to the speed of light were first predicted to jitter violently as they moved  a phenomenon known as the Zitterbewegung  in 1930, by the father of quantum mechanics, Erwin Schrödinger. The prediction was based on the Dirac equation, developed by British physicist Paul Dirac in 1928, which merges quantum mechanics with special relativity to describe how particles such as electrons behave.

"The motion is particularly unexpected because there aren't any forces acting on the particle to make it quiver," says physicist Rene Gerritsma at the Institute for Quantum Optics and Quantum Information in Innsbruck, Austria.

Instead, the jitter is caused by a combination of two effects. The first is the quantum property of superposition, which allows quantum objects to be in two mutually exclusive states or positions at the same time. The second is the existence of antimatter.

When a particle is in a superposition between its matter and antimatter states, these two contradictory sides of its personality should interfere, setting the particle quivering, explains Gerritsma. However, the phenomenon has never been observed experimentally because the motion is too small and too fast to detect in real quantum systems.

"For a long time, people have debated if Zitterbewegung is a real effect or something artificial that falls out of the equation that describes the situation, the Dirac equation," says Gerritsma, "and if it is real, whether it could ever be measured."...

In a way you could say they are "simulating" it, but only in the sense that they are using a different set up, but one which is described by the same equiations. The "solution" on that "analog" exhibits the real physical behavior of the original. So yes they are testing the theory. But not quite the original prediction.

Another way of looking at what they did is to look at their experimental set up as an analog computer which solves the same Dirac equation, suitably scaled I'm sure, as the original near light speed particle behavior. So the only question would be, does the Dirac equation properly describe the original situation.

5
posted on 01/06/2010 10:52:38 PM PST
by El Gato
("The Second Amendment is the RESET button of the United States Constitution." -- Doug McKay)

I mean F = ma doesn't even hold together when you approach the speed of light. Actually, if you re-write a bit as F= d(mv)/dt is does. where d()/dt indicates the derivative (rate of change) with respect to time. mv indicates mass times velocity or momentum. At v< F=m*dv/dt and dv/dt is just accelleration, a. Thus F = ma is merely the low speed approximation to the proper equation, which is a bit more complicated since mass becomes a function of velocity.

13
posted on 01/07/2010 4:02:07 PM PST
by El Gato
("The Second Amendment is the RESET button of the United States Constitution." -- Doug McKay)

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